1. Field of the Invention
The invention relates to the field of electronic scanning antennas.
2. Description of Related Art
Conventionally electronic scanning is obtained by means of a network antenna, each element of which is provided with a respective controlled phase shifter (or with a line of programmable length). The adjustment of the phase shifts makes it possible to aim the beam of the antenna in any desired direction within a two-dimensional angular field, defined in relation to two perpendicular planes which are frequently two planes of symmetry of the antenna.
For some applications, (antennas that are transmitters and receivers at the same time), the phase shifters must be reciprocal; this means that the phase shift is the same for the transmitted signals and for the received signals which travel in the phase shifter in a direction opposite to the first.
These technologies are well tried, but they are complex and onerous in a way that rapidly increases with the size desired for the antenna. It follows from this that the electronic scanning cannot be used in applications where it would, nevertheless, be worthwhile.
Apart from conventional phase shifters, other means have been envisaged, without so far having been capable of giving really satisfactory results.